This invention pertains generally to solid-state radio frequency transmitters and particularly to transmitters of such type wherein energy generated by each one of a plurality of diode oscillators is combined to increase the level of the transmitted energy.
It is known in the art that diode oscillators, such as those using IMPATT diodes, may be arranged in an appropriate manner to combine the outputs of a plurality of such oscillators. Thus, as shown in U.S. Pat. No. 3,931,587, a plurality of coaxial oscillator circuits (each having an IMPATT diode as the source of continuous wave (CW) radio frequency energy) is disposed around the periphery of a cylindrical cavity so that, when such cavity is operated in the TM.sub.010 mode, the CW radio frequency energy out of the coaxial oscillator circuits may be accumulated. Further, in the pending application, Ser. No. 814,743, entitled "Cylindrical Cavity Power Combiner for a Plurality of Coaxial Oscillators," Inventor George Jerinic, filed June 30, 1977, and assigned to the same assignee as this application, a similar arrangement is shown whereby pulses of radio frequency energy may be produced by injection-locking a plurality of coaxial oscillator circuits. In either arrangement, the number of coaxial oscillator circuits of a given size which may be disposed around the periphery of a cylindrical cavity is ultimately determined by the circumference of such cavity. That is to say, the amount of radio frequency energy which may be accumulated in the cylindrical cavity ultimately is limited by the number of coaxial oscillator circuits which may be located around the periphery of such a cavity.
Although it is, in theory at least, feasible to increase the number of coaxial oscillators in either of the just-mentioned arrangements by dimensioning the cylindrical cavity so that it may be operated in a higher mode, such an approach in practice has proven difficult to implement in a satisfactory manner. If, for example, the cylindrical cavity is dimensioned to support the TM.sub.020 mode, then some mode suppression means must be provided to prevent the undesired modes such as the TM.sub.210 and TM.sub.110 modes from existing. Any such means obviously increases the overall complexity of the arrangement and introduces some power dissipative elements in the cylindrical cavity which, in turn, reduce the efficiency with which the radio frequency energy from the coaxial oscillator circuits is combined.